Radiofrequency system



Dec. 29, 1925- H. F. ELLIOTT ET AL RADIO FREQUENCY SYSTEM Filed Jan. 9,1922 l HHHHHH [UN] I UH!) I (/5 WITNESS 5W Wm 1M6 H MMWW% Patented Dec.29, 1925. I

J umrsosmrss mmorm r. nmirorran'n JAMES ARTHUR, muss; or P O ALTO,qamroama; As;

sIGNons, BY mnsrnsssmmmms; 'ro FEDERAL TEIJEGRAFH'COTMPANY, orsufrmcrsco', CALIFORNIA, a CORPORATION OFCALIFORNIAl mmorancunncrsYs'rEm To: all evhom it. y concern:

, ioi-nt of operation is due in a-measureto Be it known that wax HAROLF. ELLIOT' ie transformeraction of the circuits inand J AMnsAR'rHURMInLnR, citizens of thr United States, and residing at 'Palo Alto, in

5 the: county of Santa Clara and Stateof California, have invented "acertain new and useful Radiofrequency System, of'which the followingisaspecification.-

Our. invention relates to radio frequency systems, andmore-particularlyto systems in. which are utilized arcs for converting electric energyinthe form ofdirectcur rent o'r of low frequency current into elec-'trical energy in the form of high frequency current, suitable-for:radio signaling or other uses. f c

In such systems the conversion of energy is attended with lossesinherent in the manner of; operation of the arc. The efliciency atwhichthe arc operatesis' dependent in a great measure upon the ratiobetweentheeffecti-ve value of the currentthrough the arc and the E. M.'F.across iti The ratio is in turn determined by the so-call'ed currentl5 voltage characteristic of the are, which determines what the: F. mustbe if the current is known, OI 'fVlCG versa.' It has been attempted inthe past to; control the point of operationof the arc as regards itscurrent voltage characteristic, and thus to fix the operation'ofthe arcatthe most efficient point. the patent granted to Leonard F. Fuller,Reissue No. 14,760 reissued November 25, I5 1919, entitled Wirelesstelegraphyf The scheme'involves the useof a special= circuit dertheoperation of the are as efiicient as possible.--

Investigationscf' such schemes as that sho wn inthe Fuller patentreferred to hereinbefore indicate that" the control of the Sucha schemeis 'shown in olved." Thus the primary or input circuit .nay beconsidered the antenna circuit to gether with the condenser in the arccircuit; thesecondary, as this condenser and the" condenser which is inthe branchcircuit. This secondary circuit is thus coupled to the maincircuit. The condenser in the arc circuit is common to both the primaryand the secondary. Current in the primarymade to form a secondarycircuit by beingshunted across the arc, which reactance may be eithercapacltive or inductive; A reactance i also placed in the primarycircuit which includes; the arc, which reactance is common to -both theprimary and secondary.

By properlyproportioning the ratio of the reactance in the two branches,it is possible to cause any portion of the load to flow through theauxiliary-branch circuit. For

all practical purposes, it may bestated that the currents obey the lawthat'in the two circuits they are'to each other in inverse ratio to theimpedance of' the circuits; thus when the impedance of the branchcircuit is low relatively to that o'f the arc circuit, the ratio of thetotal current to the are current is high; in other words, the ratio oftransformation is high. The system when operating at a high ratio oftransfor'n'iation has a tendency 'to become unstable. The instabilitymay result in a tendency for the arc to operate at a frequency otherthan that desired,or in a tendency for cross currents to flow betweenthe arc and the branched secondary circuit; Under such circumstances, Wehave found it advisable to use some kind of a stabilizer in "order toprevent local or cross currents between the circuits as well as toconfine the frequency of operationto a definite value.

The: invention possesses other advantagems-features, some 'ofWhiclnwith'the foregoing, will be set forth at length in the fob lowingdescription, where there will be outlined in full those forms of theinvention which we have selected for illustration in the drawingsaccompanying and forming part of the present specification. In thedrawings are shown several embodiments of our invention, but it is to beunderstood that we do not limitourselv es to such forms, since theinvention, as expressed in the claims, may be embodied in other forms aswell.

Referring to the drawings:

Figure 1 is a wiring diagram of one embodiment of our invention, inwhich capacitive r'eactances are used in the branch circuits;

Fig. 2 is a wiring diagram of a modified form of our invention, in whichinductive reactances are used in thebranch circuits;

and I i 7 Fig. 3 is a further modification bringing out more clearly theprinciples of operation involved.

In Fig. 1, the arc converter 11 is fed from mains 12 'and 13 which carryeither direct current or low frequency alternating current. Theload'circuit' in the presentinstance includes the antenna 1 1, inductor19, and the ground 15. A part only of the load current passes throughthe are 11 and a reactance 16, in this case capacitive, in seriestherewith. The remainder passes through a branch or secondary circuitwhich also" includes a capacitive reactance 17. As is :ustomary, anelectromagnet 18 of the proper strength is provided for influencing thearc. The reactances 16 and 17 are so proportioned that the desired'current-voltage ratio or transformation ratio is obtained at the are-11. The condensers 16 and 17 form substantially all of the impedances ofthe branch circuits. To stablize the circuit and make it possible toobtain'values of currentvoltage ratios otherwise unattainable, weprovide a stablizing means 20. This is shown as consisting of two coils21 and 22, one in each of the branch circuits, and so arranged on acommon iron core 23 that their magnetizing forces substantially canceleach other while no local or cross currents exist between the two branchcircuits. When such local currents attempt to flow, there results asubstantial magnetizing force, as is evident, and thus a correspondinglgreat core loss in the core 23. Since the currents normally choose suchconditions of operation that there is the least energy loss, the crosscurrents can subsist for but a short period of time and cannot riseabove a very small value. This means for stablizing as well as otherforms which may be substituted therefor, are described and claimed in aco-pending application, Serial No. 527,885., in our names entitled Radiofrequency system, filed Jan. 9, 1922, and assigned to the same assigneeas the present application.

result maybe obtained with inductive reactances. Such an arrangement isshown in Fig. 2 where the inductors 24 and 25 are inserted in each ofthe branch circuits. The are 11 sets up oscillations as before, and thehigh frequency current is made use of in the antenna signaling circuitcomprising the antenna 14, coil 19, and the ground 15. The stabilizer 20may also be used with the circuit. In this modification, the inductivereactances 24 and 25 may constitute the major portion of the inductanceof the oscillating circuit. It is necessary, in case no condensers areused in the stabilizing circuit 20, to provide a stopping condenser 26in one of the branch circuits to prevent current from the source fromcirculating through the reactances 24 and 25.

The principle of transformer action is well exemplified in Fig. 3, inwhich a furtherrnodification is shown; The inductor 27, condenser 28,and coil 30 are connected in series to the are 11, and constitute theprimary circuit. The secondary circuit comprises the earth connection15, the lower portion of coil 30, the loading inductor 19 if necessary,and the antenna 1 1. It is thus seen that the coil 30 is used as anauto-transformer, although, as is self evident, a conventional type oftransformer may be substituted therefor. By .the aid of a single coil,as 30,instead of separate primary and secondary coils, closer couplingis effected with attendant increase in efficiency.

It has been found, however, and may be readily checked mathematicallythat such a closely-coupled circuit is resonant to two isolatedfrequencies. The inductor 27, condenser 28, and the resistance 29 areintroduced into the circuit to stabilize the system and insure operationat the desired frequency. The inductor 27 and condenser 28 are for thispurpose tuned to make that portion of the circuit bridged by theresistance 29 resonant at the desired frequency. That is to say, at thatfrequency, the impedance drop across are 11, inductor 27, and condenser28 is a minimum. Under this condition of operation, the energydissipated in the resistance is a minimum. An appreciable deviation fromthe desired frequency causes a substantial increase in the energydissipated. Since the system inherently tends to operate under suchconditions that there is least energy loss, there is an immediate returnto the desired frequency.

One of the advantages attendant upon the use of this invention is thatthe current through the source is reduced, and smaller capacitysignaling circuits may be used, as well as the apparatus in thecircuits.

We claim:

1. In a radio frequency electrical system, a source of high frequencyoscillations, a load circuit supplied from said source, a circuitoffering a path for the load current free of the source, said pathserving to increase the efficiency of the source and consisting solelyof impedance, and means cooperatin with said impedance for preventingthe CW of any local currents between the source and the path.

2. In a radio frequency'electrical system,

an arc converter, a load circuit supplied from the converter, a circuitoffering a path for the load currentfree of the converter and serving toincrease the efiiciency of the arc operation, said path consisting onlyof impedance, and means cooperating with said impedance forpreventing-the flow if local currents between the converter and saidpath.

3. In a radio frequency electrical system, an arc converter, a loadcircuit supplied from the arc converter, a circuit paralleling the arcconverter consisting only of impedance, for, increasing the efiiciencyof the arc operation, and a stabilizer for preventing the flow of localcurrents between the converter and said path, comprising an energyconsuming device arranged to increase the energy loss therein upon theoccurrence of such local currents.

4. In a radio frequency electrical system, a radio frequency arc, acircuit paralleling the arc circuit and offering a path free of the arefor a portion of the load current, the impedances of the two circuitsbeing fixed at such values that the arc operates at a relativelyefiicient part of its currentvoltage characteristic, and means forpreventing the flow of any local currents between the parallel paths. 7

5. In a radio frequency electrical system, an arc converter, a loadcircuit supplied from the arc converter, a circuit paralleling the arcconverter consisting only of impe'dance, for increasing the eificiencyof the arc operation, and a resistor connecting a point in the parallelcircuit to a point in the arc converter branch for increasing the energyloss upon the occurrence of local currents between the parallelingcircuit and the arc converter.

6. In a radio frequency electrical system,

an arc converter, a tuned circuit in series with the converter, animpedance also in series with the converter, a load circuit closelycoupled to the impedance, and a resistor connected in parallel to theimpedance.

7. In a radio frequency electrical system, a radio frequency are, anoscillatory circuit connected to the arc, a circuit consisting substantially entirely of inductive reactance paralleling the arc circuitand o-ifering a path free of the arc for a portion of the load current,an inductive reactance in the arc branch circuit, forming substantiallyall of the impedance of that circuit, the impedances of the two branchedcircuits being fixed at such values that the arc operates at arelatively eflicient part of its currentvoltage characteristic, andmeans for preventing the flow of any local currents between the parallelbranch circuits.

In testimony whereof, we have hereunto set our hands.

HAROLD F. ELLIOTT. JAMES ARTHUR MILLER.

